1. Field of the Invention
The present invention relates to an extremely high frequency oscillator and, more particularly to an extremely high frequency oscillator having a high frequency circuit assembly comprising a resonant cavity and a waveguide, wherein each electron gyrating within a DC magnetic field interacts with TE-mode electromagnetic waves propagating within the high frequency circuit assembly, thereby to oscillate electromagnetic waves having wavelengths in the order of millimeters to submillimeters.
2. Description of the Related Art
One of the known electron tubes of this type is a peniotron. As is disclosed in Japanese Patent Publication No. 45-35334 and Japanese Patent Disclosure No. 61-273833, a peniotron is a high power electron tube which comprises a high frequency circuit assembly and oscillates or amplifies electromagnetic waves by virtue of the phase-separation effect resulting from the interaction between electrons gyrating within a DC magnetic field and the electromagnetic waves propagating within the circuit assembly.
The peniotron utilizes the effect resulting from the movements of guiding centers around which electrons gyrate in a spatially non-uniform, high frequency electromagnetic field. Each electron is alternately accelerated and decelerated every time it gyrates around the guiding center. The accelerations and decelerations of each electron are gradually accumulated. In this interaction, the successive deceleration is stronger than the previous acceleration. A kinetic energy of each electron corresponding to accumulated deceleration is converted into the high frequency electromagnetic energy. The essential feature of the operating mechanism of the peniotron is the energy exchange between the individual electrons and the high frequency electromagnetic field. The operating mechanism of the peniotron is basically different from that of the klystron or the gyrotron in which the electromagnetic field is amplified or oscillated because a bunching of electrons interacts with the electromagnetic field. Hence, the peniotron can perform an operation wherein electrons act, independent of a phase relationship between the electrons and the high frequency electromagnetic field. All of the electrons are therefore trapped within the deceleration electric field of the electromagnetic waves due to the phase-separation effect. In theory, all gyrating kinetic energy of the electrons can be converted into the energy of the electromagnetic waves. In view of this, the efficiency of the energy conversion, from the electrons to the electromagnetic waves, can be expected to be extremely high.
The conventional oscillator, described above cannot convert the kinetic energy acting in the longitudinal direction of the tube into the energy of electromagnetic waves. It is impossible with the prior-art oscillator to increase the energy-conversion efficiency to a near-100% value, unless the oscillator is equipped with a perfect depressed collector. Another problem with the conventional oscillator is that the higher the frequency of the electromagnetic waves, the smaller the resonant cavity and waveguide of the high frequency circuit assembly should be. The smaller the resonant cavity and the waveguide, the lower the electric power capacity, because a permissible electric power loss of the circuit is restricted. Further, the oscillator requires an intense DC magnetic field, and the frequency of the electromagnetic waves is limited. The oscillators, developed thus far, can output 10 kW at an operating frequency of 45 GHz at best.